A drill disclosed in Japanese Unexamined Patent Application Publication No. 2004-34202A (Patent Document 1) is known as a drill conventionally used for cutting a work material, such as a metal member and the like. In the drill disclosed in Patent Document 1, a part of a chisel edge smoothly connected to a main cutting edge is removed by x-type thinning so that the drill has a second cutting edge that functions as a thinning cutting edge. According to this, as the cutting speed of the main cutting edge is faster than that of the chisel edge including the thinning cutting edge, chips generated by the chisel edge are pulled by chips generated by the main cutting edge. As a result, cracks are generated in the chips generated by the chisel edge, and it is thus possible to fragment the chips into fine pieces.
In recent years, in such a case when a cutting tool is used for deep hole drilling in which the depth of the drilled hole is large with respect to the tool diameter, it is necessary to improve the durability of the cutting tool. Therefore, countermeasures, such as making the web thickness of the drill body thicker, have been considered. However, when the web thickness of the drill body is made thicker, the flute becomes shallower. As a result, the pulling force of the chips generated by the main cutting edge, which pulls the chips generated by the chisel edge including the thinning cutting edge, becomes smaller. Thus, the chips are less likely to be fragmented and tend to become long, and there is a risk that the chips may become clogged in the flute.
In light of the foregoing, an object of the present invention is to provide a drill that is capable of fragmenting chips in a favorable manner even when a web thickness of a drill body is made thicker.